Valve Regulated Lead Acid (VRLA) batteries have been increasingly deployed in outdoor telecommunications applications as a source of energy when a primary source of power is interrupted. Commonly, the lead acid batteries are referred to as "starved electrolyte" batteries, since the batteries have less acid electrolytes in comparison to batteries of the past. Batteries of this nature contain a specified amount of water as a main component. Underfilling or overfilling the batteries with water may cause a decrease in performance, capacity and lifetime.
Employed in reserve power supplies, a plurality of batteries are often coupled together into battery strings. In practice, the battery strings are constantly in a state of slight charging. Through a variety of techniques, a voltage is supplied to maintain the batteries in a fully charged state. These techniques include, among others, float, boost, equalize and intermittent charging.
At present, the capacity and reserve time of the entire string is monitored because it is very expensive to monitor the charges on the individual batteries. As a result, when a battery string loses reserve capacity, the common practice is to replace the entire string rather than a number of single batteries which may be the cause of the power loss. Due to this replacement practice, perfectly good batteries may be pulled from service. If the condition of the individual batteries could be measured or predicted, a great deal of time and money could be saved since only the failed batteries would be replaced.
In warm climates, high, uncontrolled temperatures have been found to significantly shorten the life of the battery. It is not uncommon, in these environments, for the battery life to be nearly half of its normal value. The deterioration has several root causes, namely, grid corrosion, valve design and plastic jar material selection. Ultimately, the root causes lead to water loss which causes severe damage in the VRLA batteries. Replenishing the water on a regular basis is the best method for avoiding this type of damage. At present, refilling the VRLA batteries is extremely difficult and expensive and can only be accomplished manually. There is a great need to replenish the lost water in an automated and controlled manner to extend the life of the battery.
Not only has the outdoor uncontrolled temperature profile caused a reduction in the battery life, it has resulted in great uncertainty in estimating the battery life and the available capacity in the battery. Although algorithms are available to predict the battery capacity, a monitoring system is needed to collect the necessary information for the calculation. To reduce installation time, it is desirable to have an electronic monitoring system built into the battery to perform the capacity calculation locally. The result is a monitoring system that can identify the condition of each individual battery.
Accordingly, what is needed in the art is a system for maintaining the fill fluid level of a battery that overcomes the deficiencies in the prior art.